demo: Fix strict aliasing issues with gcc-7.3

hashRange reads unsigned int from the given byte range, which violates
strict aliasing as they refer to floats. Work around this by using the
union hack (which technically violates strict aliasing, but is blessed
by gcc).

demo/main.cpp

@@ -60,14 +60,10 @@ struct Mesh
 	std::vector<unsigned int> indices;
 };
 
-struct Triangle
+union Triangle
 {
 	Vertex v[3];
-
-	bool operator<(const Triangle& other) const
-	{
-		return memcmp(v, other.v, sizeof(Triangle)) < 0;
-	}
+	char data[sizeof(Vertex)*3];
 };
 
 Mesh generatePlane(unsigned int N)
@@ -245,7 +241,7 @@ unsigned int hashMesh(const Mesh& mesh)
 		// skip degenerate triangles since some algorithms don't preserve them
 		if (rotateTriangle(t))
 		{
-			unsigned int hash = hashRange(reinterpret_cast<const char*>(&t), sizeof(t));
+			unsigned int hash = hashRange(t.data, sizeof(t.data));
 
 			h1 ^= hash;
 			h2 += hash;